As CO2 permselective membranes which can be used to separate CO2 from mixture gases by selectively permeating CO2, various polymeric membranes have been developed (for example, Non-Patent Literature 1). However, polymeric membranes generally physically permeate CO2 based on solution diffusion mechanism, and thus, there is a limitation of the improvements in CO2 permeability and CO2 to N2 selectivity (CO2/N2 selectivity).
Therefore, permeable membranes, referred to as facilitated transportation membrane, which selectively permeate gases by, in addition to solution diffusion mechanism, facilitated transportation mechanism using substances referred to as “carrier” selectively reacting with CO2 have been investigated (for example, Non-Patent Literatures 2, 3). Facilitated transportation mechanism selectively permeates certain gases based on the reversible chemical reaction between certain gases and carriers in membrane. Furthermore, recently, permeable membranes using ionic liquids have been proposed as membranes intended for facilitated transportation mechanism (Non-Patent Literatures 4, 5).